Impact of pattern reconfigurable antennas on Interference Alignment over measured channels

In recent years, it has been shown that concentrating interference and desired signal into separate spaces using Interference Alignment (IA), can achieve the outer bound of the degrees of freedom for the interference channel. However, the non-orthogonality of signal and interference space limits sum capacity performance. In this paper, we present the notion that by using reconfigurable antenna based pattern diversity, the optimal channel can be realized in order to maximize the distance between the two subspaces, thereby increasing sum capacity. We experimentally validate our claim and show the benefits of pattern reconfigurability using real world channels, measured in a MIMO-OFDM interference network. We quantify the results with two different reconfigurable antenna architectures. We show that an additional 47% gain in chordal distance and 45% gain in sum capacity were achieved by exploiting pattern diversity with IA. We further show that due to optimal channel selection, the performance of IA can also be improved in a low SNR regime.